Google says Mikan was 6'10" 245, about the same size as Blake and Love. What kinda damage do you think he could do in todays league realistically?

Depends, if he "grew up" in today's time he would probably be a superstar, but if he was just plucked out of his time and put into the NBA he would probably be an average player at best, or at least until he adapted to the rule changes then suddenly blossom